It's the manual, I am searching for. Now I am able to repair my Braun A501.

Text excerpt from page 15 (click to view)

4.

REPLACING THE BATTERIES
1. Loosen the screw on the back of the unit that holds the battery compartment cover in place, and remove the cover. Screw 2. Loosen the screw that secures one of the two battery holders in place and remove the battery holder.
RESET

Caution:Be sure to remove only one battery at a time. Otherwise, you will lose all data stored in memory.

3.

Replace the old battery with a new one. Be sure that the positive (+) side of the new battery is facing up (so you can see it).

4.

Replace the battery holder and secure it by tightening its screw. â¢ Be careful that you do not overtighten the screw. Repeat Steps 2 through 4 for another battery. â¢ Be sure to replace both batteries. Never mix old batteries with new ones, and be sure to use CR2032 lithium batteries only. After you replace both batteries, replace the battery compartment cover and secure it by tightening its screw. â¢ Be careful that you do not overtighten the screw.